The mechanisms of overexpression include inactivating mutation of PTEN tumor suppressor (Lesterhuis et al., 2013; Naidoo et al., 2014) and secreting massive inflammatory cytokines by tumor cells, especially IFN-γ which induces PD-L1 expression (Naidoo et al., 2014; van Dam et al., 2014). The gene discussed is PTEN; the disease is neoplasm.